Various types of batteries have been heretofore developed, and in every battery, a packaging material is an essential member for sealing battery elements such as an electrode and an electrolyte. Metallic packaging materials have been heretofore widely used as battery packaging materials. In recent years, along with improvements in the performance of electric cars, hybrid electric cars, personal computers, cameras, mobile phones, and the like, batteries have been required to be diversified in shape, and to be thinner and lighter weight. However, the widely used metallic battery packaging materials are disadvantageous in that they have difficulty in keeping up with the diversification of shapes, and are limited in weight reduction.
Thus, a film-shaped laminate in which a base material layer/an adhesive agent layer/a barrier layer/a heat-sealable resin layer are laminated in this order has been proposed as a battery packaging material that can be readily processed into various shapes, and can achieve a thickness reduction and a weight reduction (see, for example, Patent Literature 1). This film-shaped battery packaging material is formed such that the battery elements can be sealed by heat-welding, by means of heat-sealing, the peripheral region with the heat-sealable resin layer being opposed to itself.
At the time of sealing the battery elements, the battery packaging material is molded in a mold such that a space for housing the battery elements is formed. During this molding, the battery packaging material is stretched, which is likely to cause cracks or pinholes in the barrier layer at the flange of the mold. To solve this problem, a method for improving the lubricity of the heat-sealable resin layer is known, in which the surface of the heat-sealable resin layer of the battery packaging material is coated with a lubricant, or a lubricant is added to the resin forming the heat-sealable resin layer to cause bleed-out of the lubricant on the surface. By adopting this method, the battery packaging material is readily drawn into the mold during molding, which allows the formation of cracks or pinholes in the battery packaging material to be suppressed.